A Prospective Study Comparing CSF Shunt Flow Between "Virtual Off" and "Flow Permissive" Shunt Valve Settings Using a Wireless, Noninvasive Shunt Flow Sensor

Hydrocephalus is commonly treated with surgically implanted cerebrospinal fluid (CSF) shunts that divert excess CSF from the brain to another part of the body. Shunt malfunction is a frequent complication of treatment and can result in significant morbidity if not identified and treated promptly. However, diagnosis of shunt malfunction remains challenging because patient symptoms are often nonspecific and currently available diagnostic tools have important limitations. Existing noninvasive assessments generally rely on indirect indicators of shunt function, while invasive procedures may expose patients to discomfort, infection risk, or other complications.

The Rhaeos Shunt Monitoring System (RSMS) is an investigational, wireless, noninvasive device designed to aid in the detection of flow in implanted CSF shunts. RSMS uses thermal sensing technology to evaluate CSF flow through shunt tubing by measuring temperature changes associated with fluid movement. The device is placed on the skin overlying a palpable shunt segment, typically near the clavicle, and communicates wirelessly with a tablet application to perform measurements and record results.

This study is a prospective, multicenter, open-label, blinded, observational study designed to compare the performance of RSMS with ShuntCheck III, an FDA-cleared noninvasive device indicated as an aid to the detection of flow in implanted CSF shunts. Both devices use transcutaneous thermal sensing methods to assess shunt flow, but they differ in implementation. RSMS uses a controlled heating element and wireless electronics, while ShuntCheck III uses a disposable thermosensor and cooling from an instant cold pack.

Approximately 85 pediatric and adult participants with existing ventricular CSF shunts will be enrolled. Eligible participants must have a palpable shunt segment suitable for device placement.

Participants with programmable shunt valves capable of being adjusted to a manufacturer-defined "virtual off" setting (opening pressure greater than 400 mm H₂O) will undergo device assessments after the valve has been adjusted to the virtual off setting. These participants may also undergo optional measurements at their prescribed flow-permissive ("valve normal") setting prior to valve adjustment. Participants whose valves are not adjusted will undergo measurements only at their prescribed valve setting. For each assessment, the order of RSMS and ShuntCheck III testing will be randomized. Participants and treating clinicians will remain blinded to device outputs throughout the study.

The primary goal of the study is to compare the performance of RSMS and ShuntCheck III in assessing shunt flow with flow-permissive ("valve normal") and restricted-flow ("virtual off") settings. Device performance will be evaluated using the known valve setting as the reference condition. Measurements obtained while the valve is set to the virtual off setting will serve as flow-restricted conditions, while measurements obtained at valve-normal settings will serve as flow-permissive conditions.

Secondary analyses will evaluate additional performance characteristics, including accuracy, positive predictive value, negative predictive value, receiver operating characteristic (ROC) curve analysis, measurement completion rates, and the number of measurement attempts required to obtain a successful result. Exploratory analyses will assess device performance across clinical and demographic subgroups and study-specific variables such as body position, shunt depth, valve setting, and study site.

All study procedures are conducted in conjunction with standard clinical care. Device measurements are used solely for research purposes and will not be available to treating clinicians for patient management decisions. Participants undergoing temporary valve adjustment will be monitored following restoration of their prescribed valve setting, and all participants will be monitored for adverse events associated with device use. Adverse events, device deficiencies, and protocol deviations will be documented throughout the study.

The results of this study are intended to provide clinical evidence regarding the performance of a next-generation, wireless, noninvasive shunt flow monitoring technology and to support future regulatory evaluation of the RSMS device.